The present invention relates to data display, and more particularly to a wide dynamic range vector data raster display.
Raster scanned displays, such as CRTs and LCDs, have lower peak brightness than vector scanned CRTs since they have no ability to stop the electron beam at one point. Attempting to display a representation of a complex vector-drawn CRT waveform, typical for live video, on a rasterized display results in losing detail in some parts of the image, usually by clipping the brightest parts. FIG. 1 shows a waveform image on a display without any processing—direct one-to-one mapping from a source to a display. When vector scanned and raster scanned waveform monitors are compared side-by-side, it is obvious that the brightest areas of the waveform lack detail, i.e., “clip”, on the raster displays. Adjusting the display brightness control to correct this makes the other areas of the waveform too dark. As shown in FIG. 2 the waveform image is clipped by increasing brightness of the display, resulting in more detail in dark areas while eliminating detail in light areas. Another transform function that is used is a gamma transform function, as shown in FIG. 3, that lightens the dark and medium areas, but does not clip the highlights. Unfortunately contrast is lost in the light areas of the waveform image. The transform functions for FIGS. 1, 2 and 3 are shown in FIG. 4. Some applications, especially video waveforms, require detail in all parts of the waveform at all levels of Z-axis brightness.
Currently the display is captured with a source frame buffer where the value of each pixel (address) in the source frame buffer increments every time it is calculated that a hypothetical electron beam representing the waveform would be striking that location. The desired brightness of each displayed target pixel is represented by the value of each address in the source frame buffer. These values may also be decremented with time to represent decay of a CRT. There are two problems: not enough bit depth in each accumulator to capture the full dynamic range for display; and no readily available algorithm for lowering the overall contrast of the display without also lowering the detail and perceived sharpness and clarity of the gray areas of complex waveforms. Only one-dimensional calculations, as shown in FIG. 5, are used to translate from source frame buffer pixel values to target display pixel values.
What is desired is the ability to provide a wide dynamic range vector data raster display so a viewer may see subtle detail within all the darkest and lightest parts of an image.